Atrial fibrillation alters the microRNA expression profiles of the left atria of patients with mitral stenosis

Identification of hub genes and potential ceRNA networks of diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM), a common complication of diabetes, is defined as ventricular dysfunction in the absence of underlying heart disease. Noncoding RNAs (ncRNAs), including long noncoding RNAs (lncRNAs) and microRNAs (miRNAs), play a crucial role in the development of DCM. Weighted Gene Co-Expression Network Analysis (WGCNA) was used to identify key modules in DCM-related pathways. DCM-related miRNA-mRNA network and DCM-related ceRNA network were constructed by miRNA-seq to identify hub genes in these modules. We identified five hub genes that are associated with the onset of DCM, including Troponin C1 (Tnnc1), Phospholamban (Pln), Fatty acid binding proteins 3 (Fabp3), Popeye domain containing 2 (Popdc2), and Tripartite Motif-containing Protein 63 (Trim63). miRNAs that target the hub genes were mainly involved in TGF-β and Wnt signaling pathways. GO BP enrichment analysis found these miRNAs were involved in the signaling of TGF-β and glucose homeostasis. Q-PCR results found the gene expressions of Pln, Fabp3, Trim63, Tnnc1, and Popdc2 were significantly increased in DCM. Our study identified five hub genes (Tnnc1, Pln, Fabp3, Popdc2, Trim63) whose associated ceRNA networks are responsible for the onset of DCM.

Upregulated miR-328-3p and its high risk in atrial fibrillation: A systematic review and meta-analysis with meta-regression

BACKGROUND

Several studies have shown miR-328-3p increased in atrial fibrillation (AF), but some researches indicated no difference or even decreased. This inconsistent result confuses researchers, and it is urgent to know the truth. This study is to assess the association between miR-328-3p levels in plasma/atrial tissue and patients with AF.

METHODS

PubMed, EMBASE, Scopus, Web of Science, and ProQuest were searched from inception to February 1, 2021. The standardized mean differences (SMD) with their 95% confidence interval (CI) were calculated to evaluate the association between miR-328-3p levels and AF.

RESULTS

Twelve studies met the inclusion criteria and were used for our meta-analysis. Overall, the levels of miR-328-3p were higher in patients with AF than in the control group (SMD = 0.69, 95% CI [0.10, 1.28], P = .022). After adjustment, the overall SMD was 0.82 (95% CI [0.22, 1.42], P = .007). Sensitivity analysis indicated that the results were stable, and the trim-fill analysis showed that the results were credible. Subgroup analyses showed that AF patients, n ≥ 30, various of comorbidity, articles published earlier, and Asia groups had higher levels of expression of miR-328-3p.

CONCLUSIONS

High levels of miR-328-3p are significantly associated with an increased risk of AF. It implies that miR-328-3p played an important role in diagnosis and may serve as a potential momentous, and useful biomarker to identify AF.

Biomarkers in the clinical management of patients with atrial fibrillation and heart failure

Atrial fibrillation (AF) and heart failure (HF) are two cardiovascular diseases with an increasing prevalence worldwide. These conditions share common pathophysiologiesand frequently co-exit. In fact, the occurrence of either condition can 'cause' the development of the other, creating a new patient group that demands different management strategies to that if they occur in isolation. Regardless of the temproral association of the two conditions, their presence is linked with adverse cardiovascular outcomes, increased rate of hospitalizations, and increased economic burden on healthcare systems. The use of low-cost, easily accessible and applicable biomarkers may hasten the correct diagnosis and the effective treatment of AF and HF. Both AF and HF effect multiple physiological pathways and thus a great number of biomarkers can be measured that potentially give the clinician important diagnostic and prognostic information. These will then guide patient centred therapeutic management. The current biomarkers that offer potential for guiding therapy, focus on the physiological pathways of miRNA, myocardial stretch and injury, oxidative stress, inflammation, fibrosis, coagulation and renal impairment. Each of these has different utility in current clinincal practice.

A narrative review of non-coding RNAs in atrial fibrillation: potential therapeutic targets and molecular mechanisms

Objective

This review summarizes the advances in the study of ncRNAs and atrial remodeling mechanisms to explore potential therapeutic targets and strategies for AF.

Background

Atrial fibrillation (AF) is one of the most common arrhythmias, and its morbidity and mortality rates are gradually increasing. Non-coding ribonucleic acid RNAs (ncRNAs) are transcribed from the genome and do not have the ability to be translated into proteins. A growing body of evidence has shown ncRNAs are extensively involved in the pathophysiological processes underlying AF. However, the precise molecular mechanisms of these associations have not been fully elucidated. Atrial remodeling plays a key role in the occurrence and development of AF, and includes electrical remodeling, structural remodeling, and autonomic nerve remodeling. Research has shown that ncRNA expression is altered in the plasma and tissues of AF patients that mediate cardiac excitation and arrhythmia, and is closely related to atrial remodeling.

Methods

Literatures about ncRNAs and atrial fibrillation were extensively reviewed to discuss and analyze.

Conclusions

The biology of ncRNAs represents a relatively new field of research and is still in an emerging stage. Recent studies have laid a foundation for understanding the molecular mechanisms of AF, future studies aimed at identifying how ncRNAs act on atrial fibrillation to provide potentially promising therapeutic targets for the treatment of atrial fibrillation.

Microrna: the role in the pathophysiology of atrial fibrillation and potential use as a biomarker

The aim of the study was to analyze medical literature on the role of microRNA in the pathophysiology of atrial fibrillation and the possibilities of using microRNAs as biomarkers.The analysis of modern medical literature was carried out using the PubMed – NCBI database.

Atrial fibrillation (AF) is a common and serious cardiovascular disease. The pathophysiological mechanisms underlying the development of atrial fibrillation are not entirely clear. In addition, there are no optimal biomarkers for early detection and assessment of the prognosis for patients with atrial fibrillation. Recently, the attention of researchers has been directed to the molecules of microRNA. There is a lot of evidence that they are involved in the pathogenesis of neurological, oncological, and cardiovascular diseases. This review examines the role of microRNAs in the pathophysiology of atrial fibrillation. The possibility of using microRNA as a biomarker for the diagnosis and prediction of atrial fibrillation is also discussed.MicroRNAs play a crucial role in the pathophysiology of atrial fibrillation, regulating the mechanisms of atrial remodeling, such as electrical remodeling, structural remodeling, remodeling of the autonomic nervous system, and impaired regulation of calcium levels. The stability of microRNAs and the possibility to study them in various biological fluids and tissues, including blood, make these molecules a promising diagnostic biomarker for various cardiovascular diseases. The presented data clearly indicate that AF is associated with changes in the expression level of various microRNAs, which can be quantified using a polymerase chain reaction. Further research is required to assess the role of microRNAs as biomarkers for atrial fibrillation, in particular to establish precise reference limits.

Micro-RNA 133a-3p induces repolarization abnormalities in atrial myocardium and modulates ventricular electrophysiology affecting ICa,L and Ito currents

Mir-133a-3p is the most abundant myocardial microRNA. The impact of mir-133a-3p on cardiac electrophysiology is poorly explored. In this study, we investigated the effects of mir-133a-3p on the main ionic currents critical for action potential (AP) generation and electrical activity of the heart. We used conventional ECG, sharp microelectrodes and patch-clamp to clarify a role of mir-133a-3p in normal cardiac electrophysiology in rats after in vivo and in vitro transfection. Mir-133a-3p caused no changes to pacemaker APs and automaticity in the sinoatrial node. No significant changes in heart rate (HR) were observed in vivo; however, miR transfection facilitated HR increase in response to β-adrenergic stimulation. Mir-133a-3p induced repolarization abnormalities in the atrial working myocardium and the L-type calcium current (ICa,L) was significantly increased. The main repolarization currents, including the transient outward (Ito), ultra-rapid (IK,ur), and inward rectifier (IK1) remained unaffected in atrial cardiomyocytes. Mir-133a-3p affected both ICa,L and Ito in ventricular cardiomyocytes. Systemic administration of mir-133a-3p induced QT-interval prolongation. Bioinformatic analysis revealed protein phosphatase 2 (PPP2CA/B) and Kcnd3 (encoding Kv4.3 channels generating Ito) as the main miR-133a-3p targets in the heart. No changes in mRNA expression of Cacna1c (encoding Cav1.2 channels generating ICa,L) and Kcnd3 were seen in mir-133a-3p treated rats. However, the expression of Ppp2cA, encoding PPP2CA, and Kcnip2 encoding KChIP2, a Kv4.3 regulatory protein, were significantly decreased. The accumulation of mir-133a-3p in cardiac myocytes causes chamber-specific electrophysiological changes. The suppression of PPP2CA, involved in adrenergic signal transduction, and Kchip2 may indirectly mediate mir-133a-3p-induced augmentation of ICa,L and attenuation of Ito.

Atrial Cardiomyopathy: Pathophysiology and Clinical Consequences

Around the world there are 33.5 million patients suffering from atrial fibrillation (AF) with an annual increase of 5 million cases. Most AF patients have an established form of an atrial cardiomyopathy. The concept of atrial cardiomyopathy was introduced in 2016. Thus, therapy of underlying diseases and atrial tissue changes appear as a cornerstone of AF therapy. Furthermore, therapy or prevention of atrial endocardial changes has the potential to reduce atrial thrombogenesis and thereby cerebral stroke. The present manuscript will summarize the underlying pathophysiology and remodeling processes observed in the development of an atrial cardiomyopathy, thrombogenesis, and atrial fibrillation. In particular, the impact of oxidative stress, inflammation, diabetes, and obesity will be addressed.

Transcriptome analysis reveals key pathways that vary in patients with paroxysmal and persistent atrial fibrillation

The present study evaluated mRNA and long non-coding RNA (lncRNA) expression profiles and the pathways involved in paroxysmal atrial fibrillation (ParoAF) and persistent atrial fibrillation (PersAF). Nine left atrial appendage (LAA) tissues collected from the hearts of patients with AF (patients with ParoAF=3; and patients with PersAF=3) and healthy donors (n=3) were analyzed by RNA sequencing. Differentially expressed (DE) mRNAs and lncRNAs were identified by |Log₂ fold change|>2 and P<0.05. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes pathway enrichment, protein-protein interaction network and mRNA-lncRNA interaction network analyses of DE mRNA and mRNA at the upstream/downstream of DE lncRNA were conducted. A total of 285 and 275 DE mRNAs, 575 and 583 DE lncRNAs were detected in ParoAF and PersAF samples compared with controls, respectively. PI3K/Akt and transforming growth factor-β signaling pathways were significantly enriched in the ParoAF_Control and the calcium signaling pathway was significantly enriched in the PersAF_Control. Cis and trans analyses revealed some important interactions in DE mRNAs and lncRNA, including an interaction of GPC-AS2 with dopachrome tautomerase, and phosphodiesterase 4D and cAMP-specific with XLOC_110310 and XLOC_137634. Overall, the present study provides a molecular basis for future clinical studies on ParoAF and PersAF.

Overexpression of miRNA-3613-3p Enhances the Sensitivity of Triple Negative Breast Cancer to CDK4/6 Inhibitor Palbociclib

Triple negative breast cancer (TNBC) is characterized by lack of expression of the estrogen and progesterone receptors and HER2, which are common therapeutic targets. CDK4/6 inhibitor Palbociclib has been approved as an anti-cancer agent for breast cancer. However, identifying biomarkers that predict the response to Palbociclib has always been a challenge for molecular targeted therapy. In this study, we identify microRNA as a hallmark in TNBC patients and explore if miR-3613-3p might serve as a tumor suppressor biomarker for triple negative breast cancer patients and if overexpression of miR-3613-3p could enhance the sensitivity of TNBC cells to Palbociclib. We show that the expression of miR3613-3p was down-regulated in TNBC tumors and cells, and the overexpression of miR-3613-3p in patients’ tumor tissues was clinically and pathologically correlated with favorable prognosis, such as smaller tumor size and the lower Ki-67. In vitro, overexpression of miR-3613-3p inhibited cell proliferation, induced G1 cell-cycle arrest, and enhanced the sensitivity of TNBC cells to Palbociclib treatment. In vivo study revealed that overexpression of miR-3613-3p inhibited TNBC tumorigenesis and exerted a significant inhibitory effect of Palbociclib on MDA-MB-231 cells. Mechanically, SMAD2 and EZH2 were found to be two direct targets of miR-3613-3p and mediate the proliferation of TNBC cells and the sensitivity of the cells to Palbociclib through inducing cellular senescence. Our findings suggested that miR-3613-3p acts as a cancer-suppressor miRNA in TNBC. Moreover, our study showed that miR-3613-3p might be used as a predictive biomarker for the response of TNBC to Palbociclib.

MicroRNAs: New contributors to mechano-electric coupling and atrial fibrillation

Atrial fibrillation (AF) is a multifactorial disease, which often occurs in the presence of underlying cardiac abnormalities and is supported by electrophysiological and structural alterations, generally referred to as atrial remodeling. Abnormal substrates are commonly encountered in various conditions that predispose to AF, such as hypertension, heart failure, obesity, and sleep apnea, in which atrial stretch plays a key mechanistic role. Emerging evidence suggests a role for microRNAs (small non-coding RNAs) in the pathogenesis of AF, where they can act as post-transcriptional regulators of the genes involved in atrial remodeling. This review summarizes the experimental and clinical evidence that supports the role of microRNAs in the modulation of atrial electrical and structural remodeling with a focus on overload-induced atrial alterations, and discusses the potential contribution of microRNAs to mechano-electrical coupling and AF.

The functions of LncRNA in the heart

Cardiovascular disease is a major cause of death and disability worldwide. Recently, increasing evidence has demonstrated that various lncRNAs play critical roles in the pathogenesis of cardiovascular diseases, including myocardial ischemia and reperfusion (I/R) injury. LncRNAs are transcripts longer than 200 nucleotides. They are considered a class of dynamic noncoding RNAs known to be involved in physiological and pathological conditions with regulatory and structural roles in numerous biological processes, including genomic imprinting, epigenetic regulation, cell proliferation, development, aging and apoptosis. They are emerging as potential key regulators of a variety of cardiovascular diseases. However, the roles of lncRNAs in the heart function remain largely unknown. The purpose of this review was to summarize the functions of lncRNAs in the heart and discuss the challenges and possible strategies of lncRNA research for cardiovascular disease.

Relations between plasma microRNAs, echocardiographic markers of atrial remodeling, and atrial fibrillation: Data from the Framingham Offspring study

BACKGROUND

Circulating microRNAs may reflect or influence pathological cardiac remodeling and contribute to atrial fibrillation (AF).

OBJECTIVE

The purpose of this study was to identify candidate plasma microRNAs that are associated with echocardiographic phenotypes of atrial remodeling, and incident and prevalent AF in a community-based cohort.

METHODS

We analyzed left atrial function index (LAFI) of 1788 Framingham Offspring 8 participants. We quantified expression of 339 plasma microRNAs. We examined associations between microRNA levels with LAFI and prevalent and incident AF. We constructed pathway analysis of microRNAs' predicted gene targets to identify molecular processes involved in adverse atrial remodeling in AF.

RESULTS

The mean age of the participants was 66 ± 9 years, and 54% were women. Five percent of participants had prevalent AF at the initial examination and 9% (n = 157) developed AF over a median 8.6 years of follow-up (IQR 8.1-9.2 years). Plasma microRNAs were associated with LAFI (N = 73, p<0.0001). Six of these plasma microRNAs were significantly associated with incident AF, including 4 also associated with prevalent AF (microRNAs 106b, 26a-5p, 484, 20a-5p). These microRNAs are predicted to regulate genes involved in cardiac hypertrophy, inflammation, and myocardial fibrosis.

CONCLUSIONS

Circulating microRNAs 106b, 26a-5p, 484, 20a-5p are associated with atrial remodeling and AF.

Non-coding RNAs and Atrial Fibrillation

Atrial fibrillation is the most frequent type of cardiac arrhythmia in humans, with an estimate incidence of 1-2% in the general population, rising up to 8-10% in the elderly. Cardiovascular risk factors such as diabetes, obesity, hypertension and hyperthyroidism can increase the occurrence of AF. The onset of AF triggers additional AF episodes, leading to structural and electrical remodeling of the diseased heart. Understanding the molecular bases of atrial fibrillation have greatly advance over the last decade demonstrating a pivotal role of distinct ion channels in AF pathophysiology. A new scenario has opened on the understanding of the molecular mechanisms underlying AF, with the discovery of non-coding RNAs and their wide implication in multiple disease states, including cardiac arrhythmogenic pathologies. microRNAs are small non-coding RNAs of 22-24 nucleotides that are capable of regulating gene expression by interacting with the mRNA transcript 3'UTRs and promoting mRNA degradation and/or protein translation blockage. Long non-coding RNAs are a more diverse group of non-coding RNAs, providing transcriptional and post-transcriptional roles and subclassified according to their functional properties. In this chapter we summarized current state-of-the-art knowledge on the functional of microRNAs and long non-coding RNAs as well as their cross-talk regulatory mechanisms in atrial fibrillation.

Olesen M, Hjorth Bentzen B, Schmitt N. Investigating gene-microRNA networks in atrial fibrillation patients with mitral valve regurgitation

BACKGROUND

Atrial fibrillation (AF) is predicted to affect around 17.9 million individuals in Europe by 2060. The disease is associated with severe electrical and structural remodelling of the heart, and increased the risk of stroke and heart failure. In order to improve treatment and find new drug targets, the field needs to better comprehend the exact molecular mechanisms in these remodelling processes.

OBJECTIVES

This study aims to identify gene and miRNA networks involved in the remodelling of AF hearts in AF patients with mitral valve regurgitation (MVR).

METHODS

Total RNA was extracted from right atrial biopsies from patients undergoing surgery for mitral valve replacement or repair with AF and without history of AF to test for differentially expressed genes and miRNAs using RNA-sequencing and miRNA microarray. In silico predictions were used to construct a mRNA-miRNA network including differentially expressed mRNAs and miRNAs. Gene and chromosome enrichment analysis were used to identify molecular pathways and high-density AF loci.

RESULTS

We found 644 genes and 43 miRNAs differentially expressed in AF patients compared to controls. From these lists, we identified 905 pairs of putative miRNA-mRNA interactions, including 37 miRNAs and 295 genes. Of particular note, AF-associated miR-130b-3p, miR-338-5p and miR-208a-3p were differentially expressed in our AF tissue samples. These miRNAs are predicted regulators of several differentially expressed genes associated with cardiac conduction and fibrosis. We identified two high-density AF loci in chromosomes 14q11.2 and 6p21.3.

CONCLUSIONS

AF in MVR patients is associated with down-regulation of ion channel genes and up-regulation of extracellular matrix genes. Other AF related genes are dysregulated and several are predicted to be targeted by miRNAs. Our novel miRNA-mRNA regulatory network provides new insights into the mechanisms of AF.

Prospective Advances in Non-coding RNAs Investigation

Non-coding RNAs (ncRNAs) play significant roles in numerous physiological cellular processes and molecular alterations during pathological conditions including heart diseases, cancer, immunological disorders and neurological diseases. This chapter is focusing on the basis of ncRNA relation with their functions and prospective advances in non-coding RNAs particularly miRNAs investigation in the cardiovascular disease management.The field of ncRNAs therapeutics is a very fascinating and challenging too. Scientists have opportunity to develop more advanced therapeutics as well as diagnostic approaches for cardiovascular conditions. Advanced studies are critically needed to deepen the understanding of the molecular biology, mechanism and modulation of ncRNAs and chemical formulations for managing CVDs.

The functions of microRNA-208 in the heart

Cardiovascular disease is a major chronic complication of obesity and diabetes. Due to several patients with obesity and diabetes, it is necessary to urgently explore early diagnostic biomarkers and innovative therapeutic strategies to prevent the progression of cardiovascular diseases. Recently, microRNAs (also known as miRNAs) have emerged as important players in heart disease and energy regulation. MiRNAs are a group of small, highly conserved non-coding RNA molecules that regulate gene expression by suppressing the translation of messenger RNA of target genes or by promoting mRNA degradation. These act as a class of potential biomarkers and may provide key information in diagnosing common diseases such as tumors, tissue damage, and autoimmune diseases. Among all the known miRNAs, microRNA-208 (miR-208) is specifically expressed in myocardial cells and showed close association with the development of cardiac diseases, such as myocardial hypertrophy, cardiac fibrosis, myocardial infarction, arrhythmia, and heart failure. However, the functions and underlying mechanisms of miR-208 in heart are still unclear. In this review, we highlighted the novel insights of miR-208 functions and associated mechanisms in the regulation of cardiac diseases.

MicroRNA-133 suppresses ZFHX3-dependent atrial remodelling and arrhythmia

AIM

Atrial fibrillation (AF) is an important cause of morbidity and mortality in the modern world. Loss-of-function mutation in the zinc finger homeobox 3 gene (ZFHX3) is associated with increased risk of AF. MicroRNAs (miRNAs) participate in arrhythmogenesis, and thus miRNA modulators may be applicable as therapeutic modalities for AF. However, the altered miRNA profiles after ZFHX3 knockdown (KD) remain unclear. This study aimed to analyse the changes of miRNA expression in loss-of-function of ZFHX3 and the effect of miRNA modulation on atrial arrhythmias in this model.

METHODS

We performed small RNA deep sequencing on ZFHX3-KD and control HL-1 mouse atrial myocytes. The effect of miRNAs on ZFHX3-dependent atrial arrhythmia was evaluated through in vitro and in vivo assays in mice.

RESULTS

Among the differentially expressed miRNAs, 11 were down-regulated and 6 were up-regulated after ZFHX3 KD. Quantitative real-time PCR analysis confirmed that after ZFHX3 KD, miR-133a and miR-133b were significantly down-regulated, whereas miR-184 was the most significantly up-regulated. DIANA-miRPath analysis suggested that miR-133a/b down-regulation increases the targeted signalling of miR-133 (ie, adrenergic, Wnt/calcium and fibroblast growth factor receptor 1 signalling), which could contribute to pathological remodelling of cardiomyocytes. These results were confirmed through Western blotting. After transfection of miR-133a/b mimics in ZFHX3-KD cells, miR-133a/b levels increased, accompanied by the inhibition of their target signalling. Treatment with miR-133a/b mimics diminished ZFHX3 KD-induced atrial ectopy in mice.

CONCLUSION

ZFHX3-KD promotes distinct miRNA expressional changes in atrial myocytes. MiR-133a/b mimics may reverse signalling of ZFHX3 KD-mediated cardiac remodelling and atrial arrhythmia.

Upregulation of miR-133b and miR-328 in Patients With Atrial Dilatation: Implications for Stretch-Induced Atrial Fibrillation

Atrial stretch and dilatation are common features of many clinical conditions predisposing to atrial fibrillation (AF). MicroRNAs (miRs) are emerging as potential molecular determinants of AF, but their relationship with atrial dilatation (AD) is poorly understood. The present study was designed to assess the specific miR expression profiles associated with AD in human atrial tissue. The expressions of a preselected panel of miRs, previously described as playing a role in cardiac disease, were quantified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) in atrial tissue samples from 30 cardiac surgery patients, who were characterized by different grades of AD and arrhythmic profiles. Our results showed that AD per se was associated with significant up-regulation of miR-328-3p and miR-133b (p < 0.05) with respect to controls, with a fold-change of 1.53 and 1.74, respectively. In a multivariate model including AD and AF as independent variables, miR-328-3p expression was mainly associated with AD grade (p < 0.05), while miR-133b was related to both AD (p < 0.005) and AF (p < 0.05), the two factors exerting opposite modulation effects. The presence of AF was associated with significant (p < 0.05) up-regulation of the expression level of miR-1-3p, miR-21-5p, miR-29a-3p, miR-208b-3p, and miR-590-5p. These results showed the existence of specific alterations of miR expression associated with AD, which may pave the way to future experimental studies to test the involvement of post-transcriptional mechanisms in the stretch-induced formation of a pro-arrhythmic substrate.

MicroRNAs: Emerging biomarkers for atrial fibrillation

Atrial fibrillation (AF) causes severe cardiac dysrhythmia among patients with cardiovascular diseases. AF increases the risk of stroke and heart failure and is a growing public health concern. AF is also associated with various disease conditions such as hypertension, coronary artery disease, aging, and diabetes mellitus. The mechanism underlying AF is not completely understood due to its complexity. However, experimental and clinical data have revealed that the prevalence of this disease is associated with atrial arrhythmogenic remodeling. Currently, there are no biomarkers that are available for the early diagnosis of AF. Several studies have proposed microRNAs (miRNAs) as useful biomarkers for the diagnosis of AF due to their stability and easy availability both in atrial tissue and circulating blood. miRNAs play an important role in the development of the heart. The dysregulation of miRNA expression is associated with cardiac remodeling. Genetic factors strongly contribute to the pathogenesis of AF. Recently, single nucleotide polymorphisms (SNPs) in various genes and miRNAs have been reported to be associated with AF. The aim of this review was to discuss the correlation between SNPs in miRNAs and AF, including those miRNAs that are commonly reported as potential biomarkers for AF.

Exogenous expression of miRNA-3613-3p causes APAF1 downregulation and affects several proteins involved in apoptosis in BE(2)-C human neuroblastoma cells

MicroRNAs (miRNAs) are a class of small non‑coding RNAs involved in post‑transcriptional gene regulation. Furthermore, dysregulation of miRNA expression is an important factor in the pathogenesis of neuroblastoma. Our previous study identified that overexpression of monocyte chemoattractant protein‑induced protein 1 protein led to a significant downregulation of a novel miRNA molecule, miRNA‑3613‑3p. In the present study, the potential involvement of miRNA‑3613‑3p in the cell biology of neuroblastoma was investigated. It was identified that the expression of miRNA‑3613‑3p varies among a range of human neuroblastoma cell lines. As the delineation of the functions of a miRNA requires the identification of its target genes, seven putative mRNAs that may be regulated by miRNA‑3613‑3p were selected. Furthermore, it was identified that overexpression of miRNA‑3613‑3p causes significant downregulation of several genes exhibiting tumor suppressive potential [encoding apoptotic protease‑activating factor 1 (APAF1), Dicer, DNA fragmentation factor subunit β, von Hippel‑Lindau protein and neurofibromin 1] in BE(2)‑C human neuroblastoma cells. APAF1 mRNA was the most significantly decreased transcript in the cells with miRNA‑3613‑3p overexpression. In accordance with the aforementioned results, the downregulation of cleaved caspase-9 and lack of activation of executive caspases in BE(2)‑C cells following miRNA‑3613‑3p overexpression was observed. The results of the present study suggest a potential underlying molecular mechanism of apoptosis inhibition via APAF1 downregulation in human neuroblastoma BE(2)‑C cells with miRNA‑3613‑3p overexpression.

MicroRNAs in Atrial Fibrillation: from Expression Signatures to Functional Implications

Atrial fibrillation (AF) is the most common sustained arrhythmia and is associated with pronounced morbidity and mortality. Its prevalence, expected to further increase for the forthcoming years, and associated frequent hospitalizations turn AF into a major health problem. Structural and electrical atrial remodelling underlie the substrate for AF, but the exact mechanisms driving this remodelling remain incompletely understood. Recent studies have shown that microRNAs (miRNA), short non-coding RNAs that regulate gene expression, may be involved in the pathophysiology of AF. MiRNAs have been implicated in AF-induced ion channel remodelling and fibrosis. MiRNAs could therefore provide insight into AF pathophysiology or become novel targets for therapy with miRNA mimics or anti-miRNAs. Moreover, circulating miRNAs have been suggested as a new class of diagnostic and prognostic biomarkers of AF. However, the origin and function of miRNAs in tissue and plasma frequently remain unknown and studies investigating the role of miRNAs in AF vary in design and focus and even present contradicting results. Here, we provide a systematic review of the available clinical and functional studies investigating the tissue and plasma miRNAs in AF and will thereafter discuss the potential of miRNAs as biomarkers or novel therapeutic targets in AF.

At the heart of programming: the role of micro-RNAs

Epidemiological and experimental observations tend to prove that environment, lifestyle or nutritional challenges influence heart functions together with genetic factors. Furthermore, when occurring during sensitive windows of heart development, these environmental challenges can induce an 'altered programming' of heart development and shape the future heart disease risk. In the etiology of heart diseases driven by environmental challenges, epigenetics has been highlighted as an underlying mechanism, constituting a bridge between environment and heart health. In particular, micro-RNAs which are involved in each step of heart development and functions seem to play a crucial role in the unfavorable programming of heart diseases. This review describes the latest advances in micro-RNA research in heart diseases driven by early exposure to challenges and discusses the use of micro-RNAs as potential targets in the reversal of the pathophysiology.

Analysis of the microRNA signature in left atrium from patients with valvular heart disease reveals their implications in atrial fibrillation

BACKGROUND

Among the potential factors which may contribute to the development and perpetuation of atrial fibrillation, dysregulation of miRNAs has been suggested. Thus in this study, we have quantified the basal expressions of 662 mature human miRNAs in left atrium (LA) from patients undergoing cardiac surgery for valve repair, suffering or not from atrial fibrillation (AF) by using TaqMan® Low Density arrays (v2.0).

RESULTS

Among the 299 miRNAs expressed in all patients, 42 miRNAs had altered basal expressions in patients with AF. Binding-site predictions with Targetscan (conserved sites among species) indicated that the up- and down-regulated miRNAs controlled respectively 3,310 and 5,868 genes. To identify the most relevant cellular functions under the control of the altered miRNAs, we focused on the 100 most targeted genes of each list and identified 5 functional protein-protein networks among these genes. Up-regulated networks were involved in synchronisation of circadian rythmicity and in the control of the AKT/PKC signaling pathway (i.e., proliferation/adhesion). Down-regulated networks were the IGF-1 pathway and TGF-beta signaling pathway and a network involved in RNA-mediated gene silencing, suggesting for the first time that alteration of miRNAs in AF would also perturbate the whole miRNA machinery. Then we crossed the list of miRNA predicted genes, and the list of mRNAs altered in similar patients suffering from AF and we found that respectively 44.5% and 55% of the up- and down-regulated mRNA are predicted to be conserved targets of the altered miRNAs (at least one binding site in 3'-UTR). As they were involved in the same biological processes mentioned above, these data demonstrated that a great part of the transcriptional defects previously published in LA from AF patients are likely due to defects at the post-transcriptional level and involved the miRNAs.

CONCLUSIONS

Our stringent analysis permitted us to identify highly targeted protein-protein networks under the control of miRNAs in LA and, among them, to highlight those specifically affected in AF patients with altered miRNA signature. Further studies are now required to determine whether alterations of miRNA levels in AF pathology are causal or represent an adaptation to prevent cardiac electrical and structural remodeling.

Analysis of miRNA expression profiling in human umbilical vein endothelial cells affected by heat stress

To investigate the regulation of endothelial cell (EC) microRNAs (miRNAs) altered by heat stress, miRNA microarrays and bioinformatics methods were used to determine changes in miRNA profiles and the pathophysiological characteristics of differentially expressed miRNAs. A total of 31 differentially expressed miRNAs were identified, including 20 downregulated and 11 upregulated miRNAs. Gene Ontology (GO) enrichment analysis revealed that the validated targets of the differentially expressed miRNAs were significantly enriched in gene transcription regulation. The pathways were also significantly enriched in the Kyoto Encyclopedia of Genes and Genomes analysis, and most were cancer-related, including the mitogen-activated protein kinase signaling pathway, pathways involved in cancer, the Wnt signaling pathway, the Hippo signaling pathway, proteoglycans involved in cancer and axon guidance. The miRNA-gene and miRNA-GO network analyses revealed several hub miRNAs, genes and functions. Notably, miR-3613-3p played a dominant role in both networks. MAP3K2, MGAT4A, TGFBR1, UBE2R2 and SMAD4 were most likely to be controlled by the altered miRNAs in the miRNA-gene network. The miRNA-GO network analysis revealed significantly complicated associations between miRNAs and different functions, and that the significantly enriched functions targeted by the differentially expressed miRNAs were mostly involved in regulating gene transcription. The present study demonstrated that miRNAs are involved in the pathophysiology of heat-treated ECs. Understanding the functions of miRNAs may provide novel insights into the molecular mechanisms underlying the heat-induced pathophysiology of ECs.

MicroRNAs in Valvular Heart Diseases: Potential Role as Markers and Actors of Valvular and Cardiac Remodeling

miRNAs are a class of over 5000 noncoding RNAs that regulate more than half of the protein-encoding genes by provoking their degradation or preventing their translation. miRNAs are key regulators of complex biological processes underlying several cardiovascular disorders, including left ventricular hypertrophy, ischemic heart disease, heart failure, hypertension and arrhythmias. Moreover, circulating miRNAs herald promise as biomarkers in acute myocardial infarction and heart failure. In this context, this review gives an overview of studies that suggest that miRNAs could also play a role in valvular heart diseases. This area of research is still at its infancy, and further investigations in large patient cohorts and cellular or animal models are needed to provide strong data. Most studies focused on aortic stenosis, one of the most common valvular diseases in developed countries. Profiling and functional analyses indicate that miRNAs could contribute to activation of aortic valve interstitial cells to a myofibroblast phenotype, leading to valvular fibrosis and calcification, and to pressure overload-induced myocardial remodeling and hypertrophy. Data also indicate that specific miRNA signatures, in combination with clinical and functional imaging parameters, could represent useful biomarkers of disease progression or recovery after aortic valve replacement.

Underexpression of CACNA1C Caused by Overexpression of microRNA-29a Underlies the Pathogenesis of Atrial Fibrillation

Background

The objective of this study was to investigate the molecular mechanism of atrial fibrillation (AF), as well as the negative regulatory relationship between miR-29a-3p and CACNA1C.

Material/Methods

We searched the online miRNA database (www.mirdb.org) and identified the miR-29a-3p binding sequence within the 3′-UTR of the target gene, and then conducted luciferase assay to verify it. The cells were transfected with miR-29a-3p and I_Ca,L was determined in those cells.

Results

We validated CACNA1C to be the direct target gene of miR-29a-3p. We also established the negative regulatory relationship between miR-29a-3p and CACNA1C via studying the relative luciferase activity. We also conducted real-time PCR and Western blot analysis to study the mRNA and protein expression level of CACNA1C among different groups of cells treated with scramble control, 30nM miR-29a-3p mimics, and 60nM miR-29a-3p mimics, indicating a negative regulatory relationship between miR-29a-3p and CACNA1C. We next analyzed whether miR-29a-3p transfection in cardiomyocytes produced the effects on the I_Ca,L induced by electrical remodeling, and found a tonic inhibition of I_Ba by endogenous miR-29a-3p in atrial myocytes.

Conclusions

We validated the negative regulation between miR-29a-3p and CACNA1C, and found that miR-29a-3p might a potential therapeutic target in the treatment of AF.

MicroRNA deep sequencing reveals chamber-specific miR-208 family expression patterns in the human heart

BACKGROUND

Heart chamber-specific mRNA expression patterns have been extensively studied, and dynamic changes have been reported in many cardiovascular diseases. MicroRNAs (miRNAs) are also important regulators of normal cardiac development and functions that generally suppress gene expression at the posttranscriptional level. Recent focus has been placed on circulating miRNAs as potential biomarkers for cardiac disorders. However, miRNA expression levels in human normal hearts have not been thoroughly studied, and chamber-specific miRNA expression signatures in particular remain unclear.

METHODS AND RESULTS

We performed miRNA deep sequencing on human paired left atria (LA) and ventricles (LV) under normal physiologic conditions. Among 438 miRNAs, miR-1 was the most abundant in both chambers, representing 21% of the miRNAs in LA and 26% in LV. A total of 25 miRNAs were differentially expressed between LA and LV; 14 were upregulated in LA, and 11 were highly expressed in LV. Notably, the miR-208 family in particular showed prominent chamber specificity; miR-208a-3p and miR-208a-5p were abundant in LA, whereas miR-208b-3p and miR-208b-5p were preferentially expressed in LV. Subsequent real-time polymerase chain reaction analysis validated the predominant expression of miR-208a in LA and miR-208b in LV.

CONCLUSIONS

Human atrial and ventricular tissues display characteristic miRNA expression signatures under physiological conditions. Notably, miR-208a and miR-208b show significant chamber-specificity as do their host genes, α-MHC and β-MHC, which are mainly expressed in the atria and ventricles, respectively. These findings might also serve to enhance our understanding of cardiac miRNAs and various heart diseases.

Chamber Specific Gene Expression Landscape of the Zebrafish Heart

The organization of structure and function of cardiac chambers in vertebrates is defined by chamber-specific distinct gene expression. This peculiarity and uniqueness of the genetic signatures demonstrates functional resolution attributed to the different chambers of the heart. Altered expression of the cardiac chamber genes can lead to individual chamber related dysfunctions and disease patho-physiologies. Information on transcriptional repertoire of cardiac compartments is important to understand the spectrum of chamber specific anomalies. We have carried out a genome wide transcriptome profiling study of the three cardiac chambers in the zebrafish heart using RNA sequencing. We have captured the gene expression patterns of 13,396 protein coding genes in the three cardiac chambers—atrium, ventricle and bulbus arteriosus. Of these, 7,260 known protein coding genes are highly expressed (≥10 FPKM) in the zebrafish heart. Thus, this study represents nearly an all-inclusive information on the zebrafish cardiac transcriptome. In this study, a total of 96 differentially expressed genes across the three cardiac chambers in zebrafish were identified. The atrium, ventricle and bulbus arteriosus displayed 20, 32 and 44 uniquely expressing genes respectively. We validated the expression of predicted chamber-restricted genes using independent semi-quantitative and qualitative experimental techniques. In addition, we identified 23 putative novel protein coding genes that are specifically restricted to the ventricle and not in the atrium or bulbus arteriosus. In our knowledge, these 23 novel genes have either not been investigated in detail or are sparsely studied. The transcriptome identified in this study includes 68 differentially expressing zebrafish cardiac chamber genes that have a human ortholog. We also carried out spatiotemporal gene expression profiling of the 96 differentially expressed genes throughout the three cardiac chambers in 11 developmental stages and 6 tissue types of zebrafish. We hypothesize that clustering the differentially expressed genes with both known and unknown functions will deliver detailed insights on fundamental gene networks that are important for the development and specification of the cardiac chambers. It is also postulated that this transcriptome atlas will help utilize zebrafish in a better way as a model for studying cardiac development and to explore functional role of gene networks in cardiac disease pathogenesis.

Monocyte Chemoattractant Protein-Induced Protein 1 Overexpression Modulates Transcriptome, Including MicroRNA, in Human Neuroblastoma Cells

The recently discovered MCPIP1 (monocyte chemoattractant protein-induced protein 1), a multidomain protein encoded by the MCPIP1 (ZC3H12A) gene, has been described as a new differentiation factor, a ribonuclease, and a deubiquitination-supporting factor. However, its role in cancer is poorly recognized. Our recent analysis of microarrays data showed a lack of expression of the MCPIP1 transcript in primary neuroblastoma, the most common extracranial solid tumor in children. Additionally, enforced expression of the MCPIP1 gene in BE(2)-C cells caused a significant decrease in neuroblastoma proliferation and viability. Aim of the present study was to further investigate the role of MCPIP1 in neuroblastoma, using expression DNA microarrays and microRNA microarrays. Transient transfections of BE(2)-C cells were used for overexpression of either wild type of MCPIP1 (MCPIP1-wt) or its RN-ase defective mutant (MCPIP1-ΔPIN). We have analyzed changes of transcriptome and next, we have used qRT-PCR to verify mRNA levels of selected genes responding to MCPIP1 overexpression. Additionally, protein levels were determined for some of the selected genes. The choline transporter, CTL1, encoded by the SLC44A1 gene, was significantly repressed at the specific mRNA and protein levels and most importantly this translated into a decreased choline transport in MCPIP1-overexpressing cells. Then, we have found microRNA-3613-3p as the mostly altered in the pools of cells overexpressing the wild type MCPIP1. Next, we analyzed the predicted targets of the miR-3613-3p and validated them using qRT-PCR and western blot. These results indicate that the expression of miR-3613-3p might be regulated by MCPIP1 by cleavage of its precursor form.

Identification of microRNA-mRNA dysregulations in paroxysmal atrial fibrillation

BACKGROUND

The molecular mechanisms underlying the early development of atrial fibrillation (AF) remain poorly understood. Emerging evidence suggests that abnormal epigenetic modulation via microRNAs (miRNAs) might be involved in the pathogenesis of paroxysmal AF (pAF).

OBJECTIVE

To identify key molecular changes associated with pAF, we conducted state-of-the-art transcriptomic studies to identify the abnormal miRNA-mRNA interactions potentially driving AF development.

METHODS

High-quality total RNA including miRNA was isolated from atrial biopsies of age-matched and sex-matched pAF patients and control patients in sinus rhythm (SR; n=4 per group) and used for RNA-sequencing and miRNA microarray. Results were analyzed bioinformatically and validated using quantitative real-time (qRT)-PCR and 3'UTR luciferase reporter assays.

RESULTS

113 genes and 49 miRNAs were differentially expressed (DE) in pAF versus SR patients. Gene ontology analysis revealed that most of the DE genes were involved in the "gonadotropin releasing hormone receptor pathway" and "p53 pathway". Of these DE genes, bioinformatic analyses identified 23 pairs of putative miRNA-mRNA interactions that were altered in pAF (involving 15 miRNAs and 17 mRNAs). Using qRT-PCR and 3'UTR luciferase reporter assays, the interaction between upregulation of miR-199a-5p and downregulation of FKBP5 was confirmed in samples from pAF patients.

CONCLUSION

Our combined transcriptomic analysis and miRNA microarray study of atrial samples from pAF patients revealed novel pathways and miRNA-mRNA regulations that may be relevant in the development of pAF. Future studies are required to investigate the potential involvement of the gonadotropin releasing hormone receptor and p53 pathways in AF pathogenesis.

Advances in exploring the role of microRNAs in the pathogenesis, diagnosis and therapy of cardiac diseases in China

Cardiovascular disease has become the most serious health threat and represents the major cause of morbidity and mortality in China, as in other industrialized nations. During the past few decades, China's economic boom has tremendously improved people's standard of living but has also changed their lifestyle, increasing the prevalence of cardiovascular disease, the so-called 'disease of modern civilization'. This new trend has attracted a significant amount of research. Many of the studies conducted by Chinese investigators are orientated towards understanding the molecular mechanisms of cardiovascular disease. At the molecular level, the long-standing consensus is that cardiovascular disease is associated with a sequence mutation (genetic anomaly) and expression deregulation (epigenetic disorder) of protein-coding genes. However, new research data have established the non-protein-coding genes microRNAs (miRNAs) as a central regulator of the pathogenesis of cardiac disease and a potential new therapeutic target for cardiovascular disease. These small non-coding RNAs have also been subjected to extensive, rigorous investigations by Chinese researchers. Over the years, a large body of studies on miRNAs in cardiovascular disease has been conducted by Chinese investigators, yielding fruitful research results and a better understanding of miRNAs as a new level of molecular mechanisms for the pathogenesis of cardiac disease. In this review, we briefly summarize the current status of research in the field of miRNAs and cardiovascular disease in China, highlighting the advances made in elucidating the role of miRNAs in various cardiac conditions, including cardiac arrhythmia, myocardial ischaemia, cardiac hypertrophy and heart failure. We have also examined the potential of miRNAs as novel diagnostic biomarkers and therapeutic targets.

Redox control of cardiac remodeling in atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice and is a potential cause of thromboembolic events. AF induces significant changes in the electrophysiological properties of atrial myocytes and causes alterations in the structure, metabolism, and function of the atrial tissue. The molecular basis for the development of structural atrial remodeling of fibrillating human atria is still not fully understood. However, increased production of reactive oxygen or nitrogen species (ROS/RNS) and the activation of specific redox-sensitive signaling pathways observed both in patients with and animal models of AF are supposed to contribute to development, progression and self-perpetuation of AF.

SCOPE OF REVIEW

The present review summarizes the sources and targets of ROS/RNS in the setting of AF and focuses on key redox-sensitive signaling pathways that are implicated in the pathogenesis of AF and function either to aggravate or protect from disease.

MAJOR CONCLUSIONS

NADPH oxidases and various mitochondrial monooxygenases are major sources of ROS during AF. Besides direct oxidative modification of e.g. ion channels and ion handling proteins that are crucially involved in action potential generation and duration, AF leads to the reversible activation of redox-sensitive signaling pathways mediated by activation of redox-regulated proteins including Nrf2, NF-κB, and CaMKII. Both processes are recognized to contribute to the formation of a substrate for AF and, thus, to increase AF inducibility and duration.

GENERAL SIGNIFICANCE

AF is a prevalent disease and due to the current demographic developments its socio-economic relevance will further increase. Improving our understanding of the role that ROS and redox-related (patho)-mechanisms play in the development and progression of AF may allow the development of a targeted therapy for AF that surpasses the efficacy of previous general anti-oxidative strategies. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation.

MicroRNAs and atrial fibrillation: mechanisms and translational potential

Atrial fibrillation (AF), the most common sustained arrhythmia in clinical practice, is an important contributor to cardiac morbidity and mortality. Pharmacological approaches currently available to treat patients with AF lack sufficient efficacy and are associated with potential adverse effects. Even though ablation is generally more effective than pharmacotherapy, this invasive procedure has considerable potential complications and is limited by long-term recurrences. Novel therapies based on the underlying molecular mechanisms of AF can provide useful alternatives to current treatments. MicroRNAs (miRNAs), endogenous short RNA sequences that regulate gene expression, have been implicated in the control of AF, providing novel insights into the molecular basis of the pathogenesis of AF and suggesting miRNA targeting as a potential approach for the management of this common arrhythmia. In this Review, we provide a comprehensive analysis of the current experimental evidence supporting miRNAs as important factors in AF and discuss their therapeutic implications. We first provide background information on the pathophysiology of AF and the biological determinants of miRNA synthesis and action, followed by experimental evidence for miRNA-mediated regulation of AF, and finally provide a comprehensive overview of miRNAs as potential novel therapeutic targets for AF.

Comparative expression profiles of microRNA in left and right atrial appendages from patients with rheumatic mitral valve disease exhibiting sinus rhythm or atrial fibrillation

BACKGROUND

The atrial fibrillation (AF) associated microRNAs (miRNAs) were found in the right atrium (RA) and left atrium (LA) from patients with rheumatic mitral valve disease (RMVD). However, most studies only focus on the RA; and the potential differences of AF-associated miRNAs between the RA and LA are still unknown. The aim of this study was to perform miRNA expression profiles analysis to compare the potential differences of AF-associated miRNAs in the right atrial appendages (RAA) and left atrial appendages (LAA) from RMVD patients.

METHODS

Samples tissues from the RAA and LAA were obtained from 18 RMVD patients (10 with AF) during mitral valve replacement surgery. From these tissues, miRNA expression profiles were created and analyzed using a human miRNA microarray. Then, the results were validated using qRT-PCR analysis for 12 selected miRNAs. Finally, potential targets of 10 validated miRNAs were predicted and their functions and potential pathways were analyzed using the miRFocus database.

RESULTS

In RAA, 65 AF-associated miRNAs were found and significantly dysregulated (i.e. 28 miRNAs were up-regulated and 37 were down-regulated). In LAA, 42 AF-associated miRNAs were found and significantly dysregulated (i.e. 22 miRNAs were up-regulated and 20 were down-regulated). Among these AF-associated miRNAs, 23 of them were found in both RAA and LAA, 45 of them were found only in RAA, and 19 of them were found only in LAA. Finally, 10 AF-associated miRNAs validated by qRT-PCR were similarly distributed in RAA and LAA; 3 were found in both RAA and LAA, 5 were found only in RAA, and 2 were found only in LAA. Potential miRNA targets and molecular pathways were identified.

CONCLUSIONS

We have found the different distributions of AF-associated miRNAs in the RAA and LAA from RMVD patients. This may reflect different miRNA mechanisms in AF between the RA and LA. These findings may provide new insights into the underlying mechanisms of AF in RMVD patients.